Factor out uploading routines to MediaFireUploader
Handle FileDrop uploads
File name is not required in upload/check

When hash and size are given, filename can be omitted.
Also silence pylint errors we know about and can't fix.
Don't regenerate key if we have none, print response text
Add initial set of uploader tests
Use UploadResult as upload() result

Provide additional details about upload.
Note that action will be None if no file was actually uploaded.
Add some logging, fix closing issue with BytesIO
Fix typo and UploadSession argument
Don't log response, we already log it once
Mention Uploader in README
Add more Uploader tests, cover happy paths
Add MediaFireUploader - closes #1
Clarify client differences
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